Contents

Linear case

Two nodes:

with: the determinant of the matrix.

Quadratic case

Three nodes:

Cubic case

Four nodes:

and so on... (note that the expressions for the N2, N3 and N4 can be easily obtained by swapping the x2 values for the x1 values in the first case, x3 for x1 in the second case and x4 for x1 in the last one.